Writing instrument

Abstract

An adjustable pencil for varying the pressure on a piece of lead includes a cylindrical barrel, and a guide tube containing a piece of lead disposed in the barrel. A coil spring, a rectangular channel with a plurality of stops and a follower compresses the spring for increasing or decreasing the longitudinal force applied to the lead as it engages a writing surface. A knob rotates the guide tube to open or close a pair of jaw like grips for maintaining a pre-selected length of lead extending from the tip of the pencil.

1. An adjustable pencil for varying the pressure on a piece of lead, said pencil comprising:
 an elongated cylindrical barrel having a longitudinal axis and a longitudinal passageway extending through said barrel and said barrel including a forward portion, a tip at a forward end of said forward portion and a rear portion; 
 a rod shaped piece of lead writing material disposed in said passageway and extendable outwardly from said tip; 
 means for advancing and withdrawing said piece of lead along said passageway and outwardly from said tip; 
 said means for advancing and withdrawing said piece of lead writing material includes a gripping member having a tapered internal thread and a tapered screw member having a tapered external thread for engaging and disengaging said gripping member, said gripping member fixing said lead writing material in said passageway with a portion of lead writing material extending outwardly therefrom; and 
 means including a coil spring, a longitudinally extending generally rectangular channel in said cylindrical barrel with a plurality of perpendicular stops and a follower within said channel and extending slightly therefrom for engaging said stops to thereby maintain a pre-selected force on said lead writing material. 
 
   
   
     2. An adjustable pencil for varying the pressure on a piece of lead according to  claim 1  in which said means for advancing and withdrawing said piece of lead writing material includes a knob at an opposite end of said barrel for engaging and disengaging said gripping member.